1. Field of the Invention
This invention relates to a supporting structure for furnace crowns, which structure is specially, but not exclusively, suitable for use with furnaces operated at high temperatures.
Known in the art are several methods of constructing furnace crowns, from the traditional vault type which has in its commonest form a semicircular section resting on two sidewalls. This is a set-up which has been known from ancient times and is still largely used on account of its reliability with time. However, that construction involves considerable investment costs both as regards the amount of material it requires and the complexity of its installation. The crown, in fact, must have a considerable thickness dimension and the furnace sidewalls which support the crown must be adequately sized to bear its weight. The enormous mass involved, additionally to raising the plant cost, also brings about increased operating costs, especially in connection with the furnace lighting and extinguishing steps. In such circumstances, in fact, the agent thermal capacity of the furnace load bearing structures unavoidably requires consumption of large amounts of energy before the desired operating temperature can be reached. Likewise when the furnace is to be put off for servicing purposes, a long time is expended in waiting for the furnace structures to cool down and permit access to the inner systems. This is true of continuous operation furnaces but grows in importance in the instance of discontinuous operation furnaces.
Furthermore, vault furnaces of this type, being generally lined with a refractory material of a standard variety, are liable, when operated at high temperatures, to surface pulverization of the lining material. The powder which comes off the furnace crown is dropped onto the material being fired and aggravates the finished product faults, with a consequent increase of rejects.
Also known are other methods of covering the furnace upper portion, such as by metal structures for supporting the insulating refractory portion thereof. Such structures, however, in order to withstand high temperatures, must be provided with a forced ventilation system. This involves, first of all, an increase in energy costs for thermal dispersion due to cooling by forced ventilation, and secondly, a sudden electric power outage due to incidental causes would stop the forced ventilation and result in sudden overheating of the metal portion of the furnace crown and evident risk of consequent collapsing.
2. Prior Art
It is a primary object of this invention to obviate such prior drawbacks by providing a structure which affords the possibility of forming a furnace crown from a lightweight, high temperature resisting material.
Another object of this invention is to provide for a rapidly achieved steady state operation and cooling down of the furnace. It is a further object of the invention to provide a a furnace crown structure which can be quickly erected at a reduced cost.
A not unimportant object of the invention is to provide a furnace which can reach temperatures in the 1,600.degree. C. range.
These and other objects are achieved by a furnace crown according to the invention, for high temperature firing ceramic materials, characterized in that it comprises silicon carbide beams, said beams being laid cross wise to the longitudinal axis of the furnace; said beams being laid parallel to one another at constant pitch distances apart; and the spaces defined between said beams being closed with refractory material plates.
Advantageously, said beams have a flat rest surface adapted to receive said plates.